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If you're reading this, there's a good chance you spend much of your working day and leisure time staring at a computer screen.
You probably spend less time thinking about what it's doing to your eyes.
Many people are vaguely aware, though, that all that staring isn't great — reflected in the dry, fatigued eyes they experience after a long day of work.
Staring at a screen doesn't cause problems for everyone — and there aren't great numbers on the precise proportion of people affected — but a significant number of heavy computer users experience a range of symptoms that researchers group under the umbrella phrase "computer vision syndrome."
These symptoms are not all that well studied or understood — but here's a guide to what we do know about them, why they happen, and what you can do to prevent them as much as possible.
Dry eyes and irritation
This is the most common symptom of computer vision syndrome — for many people, after staring at a computer all day, their eyes become dried out and are more easily irritated.
Why does this happen? "More than likely, it's simply due to the fact that you're reading so much," says James Sheedy, an optometry professor at Pacific University who published some of the earliest work on computer vision syndrome. "Reading demands your attention, so you forget to blink as often."
Studies have shown that when people read from computer screens, their blink rate plummets — but this also happens when people read words from a printed page. In either case, when you blink less frequently, your eyes are much more likely to become dried out.
With computers, though, this problem is exacerbated by posture. When most people stare at a computer screen, they look straight ahead, so the eye is more widely opened than when looking down at a book. This means that a greater surface area of your eye is exposed, so your natural lubrication evaporates more quickly, leading to more dryness and irritation.
Eye fatigue and difficulty focusing
Eye strain is the second-most common complaint of computer vision syndrome, and can be accompanied by headaches and pain in or around the eyes. It, too, is mainly caused by the extra work your eyes are doing as you read all day.
It's true that office workers read a lot of text before computers came around. But the sheer amount of text that many people read today — via email, the Internet, computers, and so forth — represents a dramatic departure from most of human history. This setup may increase productivity, but it dumps a lot of work on our eyes, and it takes a toll that's easy to notice at the end of a long day.
"There's nothing inherently wrong with the computer, really," says Jeffrey Anshel, an optometrist who runs a firm that consults with companies to minimize eye problems for their computer-using employees. "It's the fact that we're using them for pretty much everything."
It may also lead to a related problem: difficulty focusing. Typically, most people go through a process in their 40s or 50s in which the eye becomes less adept at adjusting its focal distance, making it difficult for them to focus on nearby objects (this is called presbyopia, and is why most people of this age and older need reading glasses).
But some doctors believe heavy computer use can cause similar problems in younger people's accommodative abilities — but for focusing on distant objects, rather than nearby ones. "I've seen many people in their 20s and 30s who have trouble keeping things focused," Sheedy says. "Commonly, when they look off in the distance, it takes a few extra seconds to become clear for them."
Unlike presbyopia, this appears to be an acute, temporary problem — it occurs in these computer users after a long day of work, and not on days when they're not staring at screens. But for some doctors, it raises a troubling question.
Do computers cause long-term eye problems?
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It's unclear whether the heavy amount of reading and other near work that people do nowadays on computers causes nearsightedness (myopia) and other long-term vision problems. This is still one of the biggest questions in the field. The proportion of Americans with myopia has climbed significantly in the past 30 years, and some eye researchers believe it's the result of us reading so much more text.
The evidence, though, is mixed. It's a tricky question to resolve in part because a controlled experiment would be so difficult — you can't exactly get a large group of people to vow to avoid computers and other digital devices over time and then compare them with a group of computer users.
Observational studies have found that, in general, people's level of education — and thus the amount of reading they've done over their lifetime — is positively correlated with their risk of myopia. But the direction of causation could go either way: They could have read more growing up, becoming both more educated and myopic, or for various reasons people prone to myopia could be more likely to read more. Some studies have suggested that both are caused by socioeconomic factors.
For what it's worth, several of the eye doctors I spoke with felt that increased computer use — both in school and in the workplace — has indisputably changed the development patterns of myopia, making it more common for people to become nearsighted in their 20s or 30s, rather than the conventional pattern of becoming myopic during childhood and stabilizing by adulthood.
How might this happen? One factor in addition to the extra work done by the eyes as they read, Anshel says, is the difference in posture between reading on a computer and reading a book. "Normally, when people read, they're looking down towards their laps. When they're looking at computer screens, it's straight out, more horizontal," he says. "And there are studies that show our focusing ability is not as accurate in that straight ahead position as it is when we're looking down." Constantly forcing our eyes to focus on small text when looking straight out could be increasing strain, eventually leading to nearsightedness.
Richard Yee, an ophthalmologist who's studied the long-term effects of computer use, has an intriguing alternate hypothesis. He believes that in some people, the combination of heavy computer use, the reduced blinking during that goes on during it, and a natural tendency toward clogging of the meibomian glands (which secrete oils present in tears) can cause long-term inflammation and dysfunction within these glands, which can be related to other chronic eye issues.
What you can do to save your eyes
The most common recommendation for protecting your eyes (without sacrificing a lifestyle heavily reliant on computers and reading, that is) is called the 20-20-20 rule, developed by Anshel.
"Basically, every 20 minutes, a person should look away from their desk for 20 seconds, and focus on something at least 20 feet away," he says. This prevents your eyes from focusing at near distances for extremely long durations, forcing them to alter their focal distance. It's also a good idea to consciously do some blinking at this sort of regular interval, in order to prevent excessive dryness.
Your desk should also be set up in a way to minimize eye stress. It's recommended that your monitor be positioned 20 to 40 inches in front of your eyes, and the top of the monitor should line up with your eye level, so you're looking down about 15 degrees when you stare at the screen.
Obviously, having the right glasses or contact lenses also matter. It's important to get regular eye exams so you have the proper level of correction to minimize eye strain — and it's been proven to be a total myth that using a lower level of correction (or not wearing glasses at all) can slow down vision loss.
